Hydrophilic porous materials are recognized as very promising materials for water-sorption-based energy storage and transformation. In this study, a porous, zeolite-like aluminophosphate with LTA (Linde Type A) topology is inspected as an energy-storage material. According to sorption and calorimetric tests, the aluminophosphate outperforms all other zeolite-like and metal-organic porous materials tested so far. It adsorbs water in an extremely narrow relative-pressure interval (0.10 ( p/p0 ( 0.15) and exhibits superior water uptake (0.42 g g-1) and energy-storage capacity (527 kW h m-3). It also shows remarkable cycling stability; after 40 cycles of adsorption/desorption its capacity drops by less than 2%. Desorption temperature for this material, which is one of crucial parameters in applications, is lower from desorption temperatures of other tested materials by 10–15 °C. On the microscopic scale, sorption mechanism in AlPO4-LTA is elucidated by X-ray diffraction, nuclear magnetic resonance measurements, and first-principles calculations. Videoabstract: https://www.youtube.com/watch?v=S2GVaWzFGkE. The research was based on our previous study published in 2012 in Advanced Functional Materials, where we predicted the required structural properties of porous materials for efficient storage of low heat with the case of aluminophosphate AlPO4-TRIC. Our predictions were confirmed by the latest research.
COBISS.SI-ID: 6070810
We introduced a new method that allows us an investigation of spatialy distributed organic linkers or functional groups within mixed-ligand metal-organic framework materials. The method greatly simplifies the determination of the linker distribution according to the previously presented procedures (marking with isotopes or studying individual parts of monocrystals by cutting a single crystal), which were both published in the journal Science. The method is based on nuclear magnetic resonance measurement of spin-diffusion rates and modelling of distributions of organic linkers within the metal-organic frameworks. It can distinguish between the cases, in which different linkers form domains, and cases, in which different linkers are uniformly distributed throughout the materials. This unique tool can be employed also for studying other heterogeneous or spatially disordered materials.
COBISS.SI-ID: 5735962
A HKUST-1 metal–organic framework was crystallized in the NH2-modified mesostructured silica FDU-12 in order to improve its structural stability upon water exposure. In-depth structural characterization studies of the designed composite confirmed successful formation of the MOF phase within the ordered spherical mesopores of the silica matrix. In spite of the confinement within the cavities, MOF exhibits full accessibility for the adsorbed gas molecules (CO2, H2, CH4). In contrast to the bulk HKUST-1, which undergoes slow phase transition in a humid environment, the structural integrity of the HKUST-1 in the humid-protective matrix remains unchanged even after immersion and stirring in water at elevated temperature.
COBISS.SI-ID: 6253850
HKUST-1(Cu) and MOF-5(Zn)@polyHIPE hybrid materials were prepared using a metal salt-free technique, wherein metal–organic frameworks were in situ generated from the CuO- and ZnO-nanoparticles through secondary recrystallization. The solid-to-MOF transformation has proven to be a feasible and effective technique for preparing MOF@polyHIPE hybrid materials with a high MOF content of more than 75 wt%. The MOF phase within the hybrid polyHIPEs as disclosed herein exhibits superior micropore accessibility, structure hydrostability and durable CO2 adsorption capacity under humid conditions, not achievable with any of the previously reported methods.
COBISS.SI-ID: 6072090
Binder-free granulated zeolite Y was post-synthetically modified to improve its low-temperature heat storage performance. Procedures such as treatment with EDTA, treatment with HCl, and ion exchange (Mg2+) with acid treatment were used. All modified samples showed a decrease in the desorption temperature from 10 to 30 °C compared to the unmodified zeolite. Only the desorption temperature of the ion-exchanged and acid-treated sample was increased. We carefully studied the effect of various treatments on the structural properties of materials, including the formation of structural defects. The energy storage density of our materials was compared with one of the currently used adsorbents (zeolite X) and an increase of up to 50% was determined.
COBISS.SI-ID: 6387482
Developing methods of NMR crystallography, we tried to identify the most accurate computational approach for the prediction of paramagnetic shifts, which can be detected in NMR spectra of paramagnetic materials because of the strong hyperfine interaction between atomic nuclei and the unpaired electrons of paramagnetic centres. We found out that the best prediction was achieved by quantum-mechanical calculations within the frame of density functional theory, with localized basis functions and hybrid exchange-correlation functional PBE0. Using this knowledge we investigated a complex metal-organic material MIL-100, in which framework metal sites were occupied by Al(III) and Fe(III) ions. With NMR measurements and DFT-based calculations, supported by other spectroscopic measurements, we were able to explain the magnetic properties of this material and to determine the distribution of Al and Fe within the framework.
COBISS.SI-ID: 32220711
Using the NMR approach, which we had developed for structural characterizations of inhomogeneous and disordered materials, studied a new type of glassy materials, consisting of metal centers and organic ligands. This is the fourth type of glass beside oxide, metallic and organic glasses, and the first type that was discovered after 1960. We prepared, for the first time, a porous glass, which could absorb notable amounts of different gases. The key element in the preparation of the porous glass was the selection of a convenient parent crystalline zinc-imidazolate material, ZIF-76, which had to contain bulky, partly-branched imidazolate ligands. After melt quenching, such bulky ligands could not densify into a non-porous glass. We also prepared and investigated a metal-organic glass from the crystalline ZIF-62, which has shown the greatest glass-forming ability among all materials inspected so far. This means that it has the highest Tg/Tm ratio, where Tm and Tg are the melting temperature of the crystalline ZIF-62 and the glass-to-liquid transition temperature of the glassy ZIF-62. Results of the two studies were described in two papers in distinguished journals, Nature Communications and Science Advances.
COBISS.SI-ID: 6532378
Different types of TiO2-SiO2 composites in the form of powder or films have been reported as efficient photocatalysts for decomposition of organic compounds in liquid and gas phase. Herein, we report for the first time on the formation of efficient TiO2-SiO2 films made from acidic organic-free colloidal solution of TiO2 anatase nanoparticles (AS) and mesoporous SiO2 (SBA-15) with 100 % loading (TiO2 : SiO2 molar ratio 1:1) under simple and low cost procedure. AS was prepared from metatitanic acid precursor using a novel, environmentally friendly approach of TiO2 nanoparticles precipitation with NaOH and peptization with HCl. These AS/SBA-15 films, immobilized by brush deposition on glass carriers, showed total decomposition of toluene and 91 % decomposition of formaldehyde as model VOCs in gas phase, at room temperature under UVA irradiation in lab-made batch photoreactor. The trend of photocatalytic efficiency for decomposition of formaldehyde was AS/SBA-15 ) P25 ) PC500 ) AS. The adsorption capability of the AS/SBA-15 was higher in comparison to its pure TiO2 analogues (AS, P25, PC500) in case of toluene. Turnover frequency (TOF) of the AS/SBA-15 was approximately six times higher in comparison to its pure TiO2 analogue AS for toluene and formaldehyde. The potential of AS/SBA-15 for the use in air cleaning devices is finally discussed.
COBISS.SI-ID: 5823258
In situ generated Ni metal nanoparticles have been insofar reported as an efficient catalyst for the tar cracking during the wood liquefaction by pyrolysis. Herein, their performance in further bio-oil conversion steps is evaluated. Nanoparticles were generated for the first time from Ni-containing metal-organic framework (MOF), MIL-77, during the hydrotreatment of glycerol-solvolysed ligniocellulosic (LC) biomass. Reactions were conducted at 300 °C and the hydrogen pressure of 8 MPa in a slurry reactor. The catalytic activity and selectivity of the deoxygenation and hydrocracking reactions for real biomass-derived feedstock was compared for the in situ generated nanoparticles and the ones, dispersed on silica–alumina support (commercial Ni/SiO2–Al2O3 catalyst). The mass activity of the in situ generated nanoparticles for hydrogenolysis was more than 10-times higher in comparison to their commercial analogues, and thus their potential for the use in LC biorefinery is finally discussed.
COBISS.SI-ID: 5667866
Titanium dioxide has been widely used as an antimicrobial agent, UVfilter and catalyst for pollution abatement. Herein, surfacemodifications with selected transition metals (Me) over colloidal TiO2 nanoparticles and immobilization with a colloidal SiO2 binder as composite films (MeTiO2/SiO2) on a glass carrier were used to enhance solar-light photoactivity. Colloidal TiO2 nanoparticles were modified by loading selected transition metals (Me 1 Mn, Fe, Co, Ni, Cu, and Zn) in the form of chlorides on their surface. They were present primarily as oxo-nanoclusters and a portion as metal oxides. The structural characteristics of bare TiO2 were preserved up to an optimal metal loading of 0.5 wt%. We have shown in situ that metaloxo-nanoclusters with a redox potential close to that of O2/O2 were able to function as co-catalysts on the TiO2 surface which was excited by solar-light irradiation. The materials were tested for photocatalytic activity by two opposite methods; one detecting O2 (reduction, Rz ink test) while the other detecting OH (oxidation, terephthalic acid test). It was shown that the enhancement of the solar-light activity of TiO2 by the deposition of transition metal oxonanoclusters on the surface depends strongly on the combination of the reduction potential of such species and appropriate band positions of their oxides. The latter prevented excessive selfrecombination of the photogenerated charge carriers by the nanoclusters in Ni and Zn modification, which was probably the case in other metal modifications. Overall, only Ni modification had a positive effect on solar photoactivity in both oxidation and reduction reactions.
COBISS.SI-ID: 6369818